1. Field of the Invention
This invention relates to an apparatus for use during the production of multifilament, synthetic yarn. In particular, it relates to a muffler, for use in conjunction with an interfloor tube and aspirator, which reduces by up to 10.DELTA.dB(A) the noise emitted at the inlet end of the interfloor tube when the aspirator is operational.
Throughout the present specification and claims, the term "dB(A)" (decibels-A-weighted) connotes a unit of measurement of sound level corrected to the A-weighted scale, as defined in ANSI S1.4-1971, using a reference level of 20 micropascals (2.times.10.sup.-5 Newtons per square meter). The term ".DELTA.dB(A)" refers to the difference between two noise levels where each level is expressed in units of dB(A). The term "yarn" is employed in a general sense to indicate strand material, either textile or otherwise, and including a continuous, often plied, strand composed of fibers, filaments, glass, metal, asbestos, paper, or plastic, or a noncontinuous strand such as staple, and the like. An "end" is one or a contiguous group of such strands of yarn. The "extrusion rate" is the number of pounds of polymer extruded per hour per position.
2. DESCRIPTION OF THE PRIOR ART
In a typical melt spinning process, one or more filaments is extruded from one or more spinnerettes and passed into a quenching chamber for cooling. Further process equipment, for instance drawing or winding apparatus, is usually spaced a considerable distance vertically downwardly therefrom. In fact, it is normal practice to have the process equipment spaced over three tiers with the extrusion apparatus occupying the uppermost tier or floor, with the quenching apparatus occupying the intermediate floor, and any further process equipment residing on the bottom floor. In order to convey the yarn from the quenching area to the bottom floor, it is conventional to provide an interfloor tube. To initiate string-up, an operator catches the advancing quenched filaments and throws them towards the entrance to the interfloor tube through which they fall to be picked up by either a string-up aspirator or a panel aspirator. An aspirator is usually employed in conjunction with the interfloor tube to accelerate the speed of the yarn to extrusion speed as the yarn does not fall fast enough due to drag. The smaller the inner diameter of the interfloor tube the greater the necessity for an aspirator due to the increased drag on the yarn. Therefore, to initiate string-up, an aspirator for use in conjunction with the interfloor tube should be turned on and remain on until the yarn end or ends thrown through the tube have been picked up by either a panel aspirator or a string-up aspirator, at which time the interfloor tube aspirator is turned off.
The aspirator is preferably located at the inlet portion of the interfloor tube where high velocity air is introduced and then directed downwardly to create the desired suction effect. Noise is produced at and downstream of the point at which this high velocity air is introduced. The sound waves thus generated are then propagated through both the inlet and exit ends of the interfloor tube. U.S. Pat. No. 4,030,651 to Weiss et al. discloses a muffler for the exit end of an interfloor tube and aspirating means. The noise emitted, as measured at a distance of about one foot (30.5 cms.) from the center line of the interfloor tube and at about 2.5 feet (76.2 cms.) above the intermediate floor and at an air supply line pressure of 100 psig, has been found to exceed 100 dB(A) in some instances without use of this invention.
The high level noise emitted from the interfloor tube inlet occurs only during string-up, and as a component in a process which has several other sources of noise, it is desirable to bring its noise level down to tolerable limits. Applicants therefore provide a muffler which reduces the noise emitted at the inlet end of the interfloor tube by up to 10.DELTA.dB(A) to thereby bring the noise within acceptable levels.